Various forms of wireless communications protocols provide an effective means for devices to quickly and easily establish communications. For example, Near Field Communication (NFC) enables communication between consumer electronics devices without the need for physical connectors and user configuration. Typically, two NFC devices communicate when they are brought together in close physical proximity or by causing them to physically touch, thus engaging the devices' interfaces and configuring them to establish a peer-to-peer network. Examples of how NFC can be used include the downloading of digital photos from a camera enabled cell phone by touching the phone to an enabled computer, television, printer, or digital picture frame, and downloading applications or games to a handheld device by touching the device to the computer.
NFC is a very short-range wireless technology with distances measured in centimeters. The devices' NFC interfaces typically connect and configure themselves automatically to form a peer-to-peer network. The communication link is typically half-duplex, using a strictly turn-taking methodology with one device sending and the other device responding with data or control information of its own before the first device may send new information. In the event that neither device has data to send, an empty frame, or symmetry primitive (SYMM) is sent. The transmission of the SYMM primitive allows the sending device to regain use of the link when the receiving device has no data to send. When neither device has data or control information to send, SYMM primitives will be sent in both directions, and the link may be said to be idle.
Active transmission requires device power, and the continuous transmission of SYMM primitives when no data is actually being exchanged represents an unnecessary drain on the battery resources of portable devices. In this case, it is desirable to maximize the turnaround time without causing a communications failure. However, when data is being transmitted, it is desirable for data throughput to be maximized by allowing the sending device to regain control of the link as soon as possible. In that case, the fastest possible turnaround time is desirable. Similar problems arise in other forms of half duplex communications links.
Therefore, what are needed are methods and systems that are able to efficiently transmit and receive without unnecessarily consuming power, thereby prolonging the battery charge. Reducing the power consumption of the device increases the time between recharging (if the battery is rechargeable) and/or increases the useful life of the battery (and in some cases the device itself) thereby prolonging periods between replacement. The methods and systems disclosed herein address these shortcomings